1. Field of the Invention
The present invention relates to a method for ionization film formation and an ionization film-formation apparatus used in manufacture of semiconductor devices, such as LSIs, recording media, such as magneto-optical disks, and the like.
2. Description of the Related Art
Various methods for film formation have been used in formation of wirings and formation of interlayer insulation films regarding various semiconductor devices and, furthermore, in formation of magnetic layers, protection layers, etc., regarding recording media. In this case, film-formation apparatuses are required to perform in various ways. Recently, improvement of a coverage property has been required on the inner surfaces of holes arranged in substrates, especially the bottom portions.
FIG. 6 shows the shape of a film deposited by a conventional sputtering method. The thickness of films 102 deposited on the groove bottom portions 104 of a substrate 8 are very small compared with the thickness of films 100 deposited on groove top portions 103, and, therefore, it is clear that the coverage is poor. It is seen that films are also deposited on the groove side surfaces 101. Degradation of the coverage property and adherence of the films onto the side surfaces adversely affects the quality of the film formation.
As an example, a magneto-optical disk of the domain wall displacement type disclosed in Japanese Patent Laid-Open No. 6-290496 will be described.
Regarding conventional magneto-optical disks and compact disks, grooves have been arranged concentrically on the disks, and the groove portions have not been used for recording information. However, regarding optical disks of the domain wall displacement type, functional films must be formed on the bottom portions of the grooves similar to flat portions (lands) other than the grooves in order to allow the bottom portions to become recording portions. Furthermore, to prevent interference between the grooves and the lands, magneto-optical signals must not be generated from the groove side surfaces, which are boundary surfaces, and the quantity of film adherence onto the groove side wall surfaces must be minimized. That is, regarding the magneto-optical disk of the domain wall displacement type, film formation with strong directivity and a high bottom coverage ratio (ratio of the film formation velocity onto the groove bottom surface to the film formation velocity onto the periphery surface of the groove) is required.
Conventionally, as a means of film formation with a high bottom coverage ratio, a low-pressure remote sputtering method disclosed in Japanese Patent Laid-Open No. 10-130832, etc., is known. The low-pressure remote sputtering method refers to a means in which sputtered particles do not scatter, but fly straight ahead because the pressure in a chamber is lowered compared with the pressure in a common sputtering method in order to increase a mean free path, and, in addition, the sputtered particles flying perpendicularly toward a substrate are allowed to deposit selectively on the substrate by increasing the distance between a target and the substrate.
Another method, a collimated sputtering method is known. In this method, a cylindrical tube (collimator) having a plurality of holes in the direction perpendicular to a substrate is arranged between a target and the substrate. Only particles flying perpendicularly toward the substrate are allowed to reach the substrate to form a film.
There is also a method for ionization film formation described in Japanese Patent Laid-Open No. 2001-152330, applied for a patent by the inventors of the present invention. In this method, a sputtering discharge gas is excited using an ionization mechanism of the hot cathode system, and is allowed to collide with sputtered particles to ionize the sputtered particles. The sputtered particles thereby ionized are directed perpendicular into the substrate by an electric field proximate to the substrate surface for deposition.
It is an object of the present invention to provide a method for ionization film formation and an ionization film-formation apparatus, each capable of forming a deposited film with a high bottom coverage ratio onto even a substrate having deep grooves on the surface.
It is another object of the present invention to provide a method for ionization film formation and an ionization film-formation apparatus, each having an improved ionization efficiency of vaporized particles by colliding metastable excited He atoms formed inside an ionization mechanism with the vaporized particles.
It is another object of the present invention to provide a method for ionization film formation and an ionization film-formation apparatus, each capable of preventing sputtering of a hot-cathode filament due to ions formed from an excited ionization gas by using He gas as the ionization gas, and, therefore, each is capable of improving the life of the hot-cathode filament significantly.
The aforementioned objects can be achieved by an ionization method for film formation. A deposited film is formed by ionizing vaporized particles with an ionization mechanism of the hot cathode system, and injecting the ionized particles into a substrate. The method includes the step of introducing He gas inside the ionization mechanism at the back of a hot-cathode filament, between the hot-cathode filament and a grid, or the like, when viewed from the center of an ionization space.
The aforementioned objects can be achieved by an apparatus for ionization film formation to form a deposited film by ionizing vaporized particles with an ionization mechanism of the hot cathode system, and injecting the ionized particles into a substrate. The apparatus has a gas introduction device to introduce an ionization gas inside the ionization mechanism at the back of a hot-cathode filament, between the hot-cathode filament and a grid, or the like, when viewed from the center of an ionization space.
In another aspect, the invention relates to an ionization film formation-method for forming a deposited film. The method comprises forming at least one of excited helium atoms and helium ions by causing helium gas to collide with thermoelectrons, and ionizing vaporized particles by colliding the vaporized particles with at least one of the excited helium atoms and the helium ions. Further, the invention preferably comprises forming the thermoelectrons by at least one filament of a hot-cathode system, directing the thermoelectrons from the filament to an ionization space by a positively charged grid, and either introducing the helium gas upstream of the filament, relative to the grid and the ionization space, or introducing the helium gas between the hot-cathode filament and the grid.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.